Unnamed Scrambler 25A p0ke

Hunt Hypothesis

This hypothesis targets the presence of obfuscated payloads utilizing Scrambler-like techniques, which adversaries employ to evade static analysis and signature-based detection. Proactively hunting for these patterns in Azure Sentinel allows the SOC to identify stealthy malware or web shell components that may have been deployed to establish persistence or execute commands within the environment.

YARA Rule

rule Unnamed_Scrambler_25A_p0ke: PEiD
{
    strings:
        $a = { 55 8B EC B9 0B 00 00 00 6A 00 6A 00 49 75 F9 51 53 56 57 B8 6C 3E 40 00 E8 F7 EA FF FF 33 C0 55 68 60 44 40 00 64 FF 30 64 89 20 BA 70 44 40 00 B8 B8 6C 40 00 E8 62 F3 FF FF 8B D8 85 DB 75 07 6A 00 E8 A1 EB FF FF BA E8 64 40 00 8B C3 8B 0D B8 6C 40 00 E8 37 D3 FF FF C7 05 BC 6C 40 00 0A 00 00 00 BB 68 6C 40 00 BE 90 6C 40 00 BF E8 64 40 00 B8 C0 6C 40 00 BA 04 00 00 00 E8 07 EC FF FF 83 3B 00 74 04 33 C0 89 03 8B D7 8B C6 E8 09 F3 FF FF 89 03 83 3B 00 0F 84 BB 04 00 00 B8 C0 6C 40 00 8B 16 E8 06 E2 FF FF B8 C0 6C 40 00 E8 24 E1 FF FF 8B D0 8B 03 8B 0E E8 D1 D2 FF FF 8B C7 A3 20 6E 40 00 8D 55 EC 33 C0 E8 0C D4 FF FF 8B 45 EC B9 1C 6E 40 00 BA 18 6E 40 00 }
        $b = { 55 8B EC B9 0B 00 00 00 6A 00 6A 00 49 75 F9 51 53 56 57 B8 6C 3E 40 00 E8 F7 EA FF FF 33 C0 55 68 60 44 40 00 64 FF 30 64 89 20 BA 70 44 40 00 B8 B8 6C 40 00 E8 62 F3 FF FF 8B D8 85 DB 75 07 6A 00 E8 A1 EB FF FF BA E8 64 40 00 8B C3 8B 0D B8 6C 40 00 E8 }
    condition:
        for any of ($*) : ( $ at pe.entry_point )

}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• PowerShell Script Obfuscation by DevOps Teams: Development or DevOps engineers may use Invoke-Obfuscation or similar community tools to obfuscate PowerShell scripts for internal automation tasks (e.g., database backups, log rotation) to hide sensitive logic or reduce script size.

  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\Dev\Scripts\) or exclude processes originating from known IDEs (e.g., code.exe, idea64.exe) when the file extension is .ps1 or .psm1.

• Commercial Application Self-Update Mechanisms: Some enterprise applications (e.g., Adobe Creative Suite, JetBrains IDEs, or specific ERP clients) use packed or obfuscated updater executables to verify integrity or protect proprietary update logic during the installation or patching process.

  • Filter/Exclusion: Whitelist specific known-good binary hashes (SHA256) for these updaters, or exclude processes running from vendor-specific update folders (e.g., C:\Program Files\Adobe\Adobe Update\, C:\Program Files\JetBrains\Updater\).

• Scheduled Task Execution of Obfuscated Maintenance Scripts: IT administrators may create scheduled tasks that run obfuscated PowerShell or Python scripts for nightly maintenance (e.g., disk cleanup, user account sync) to prevent casual inspection of complex logic or credentials.

  • Filter/Exclusion: Correlate with the parent process schtasks.exe or Task Scheduler and exclude files in standard admin script repositories (e.g., C:\Admin\Scripts\, C:\SysAdmin\Maintenance\) if the script is signed by a trusted internal certificate.

• Test Automation Frameworks (Selenium/Playwright): QA teams using browser automation tools may load obfuscated JavaScript or helper scripts to interact with